Introduction

News

• February 12, 2024: Introducing the MedVidQA 2024 challenge.

Important Dates

	Video Corpus Release	Training/Val Set Release	Test Set Release	Submission Deadline	Official Results
Task A	May 12	April 30	June 7	August 2	September 8
Task B	NA	April 30	September 2	September 16	October 11

Registration and Submission

• Participants are required to complete their registration by submitting the TREC 2024 Registration Form. Registered teams will be added to TREC 2024's mailing list for future communication.
• Submission: TBD

Tasks

• Task A: Video Corpus Visual Answer Localization (VCVAL)

  Given a medical query and a collection of videos, the task aims to retrieve the appropriate video from the video collection and then locate the temporal segments (start and end timestamps) in the video where the answer to the medical query is being shown, or the explanation is illustrated in the video.
  
  

  
  Schematic workflow of the video corpus visual answer localization task.

The VCVAL task consists of two subtasks: (a) Video Retrieval, and (b) Temporal Segment Prediction.




• Task B: Query-Focused Instructional Step Captioning (QFISC)

  Given a medical query and a video, this task aims to generate step-by-step textual summaries of the visual instructional segment that can be considered as the answer to the medical query. The proposed QFISC task can be considered an extension of the visual answer localization task, where the system needs to locate a series of instructional segments that serve as the answer to the query. The QFISC demands identifying the instructional step boundaries and generating a step caption for every step. This task comes under multimodal generation, where the system has to consider the video (visual) and subtitle (language) modality to generate the natural language caption.

Datasets

• Task A

  • Training and Validation Datasets: MedVidQA collections [1] consisting of 3,010 human-annotated instructional questions and visual answers from 900 health-related videos.

• Task B

  • Training and Validation Datasets: Open domain HIREST dataset [3] to train the system for Task B. HIREST comprises 3.4K text-video pairs sourced from an instructional video dataset. Among these, 1.1K videos are annotated with moment spans pertinent to text queries. Each moment is further dissected into key instructional steps, complete with captions and timestamps, resulting in a total of 8.6K step captions.

Evaluation Metrics

• Task A

  • The VCVAL task consists of two sub-tasks: video retrieval (VR) and visual answer localization (VAL). We will evalaute the performance of the video retrieval system in terms of Mean Average Precision (MAP), Recall@k, Precision@k, and nDCG metrics with k={5, 10}. We will follow the trec_eval evaluation library to report the performance of participating systems. For the VAL task, following MedVidQA 2023, we will use Mean Intersection over Union (mIoU) and IoU =0.3, IoU=0.5 and IoU=0.7 as the evaluation metrics.

• Task B

  • We plan to evaluate the performance of the step captioning task on two fronts: (1) how close the system-generated step caption is to the ground truth step captions, and (2) how well the predicted step segment aligns with the ground truth step segment.
    
    
    
    1. We will measure the closeness in two ways:
       1. With the help of predicted timestamps and sentence-level similarity (ROUGE-L) of the step, we will align a predicted step to one of the ground truth steps. Once a predicted or ground truth step is matched, it is no longer considered, so there will be only one-to-one matching. Towards this, we define the following:
       • TP (True Positives): Represents the count of predicted steps that are present in the ground truth steps.
       • FP (False Positives) : Represents the count of predicted steps that are not present in the ground truth steps.
       • FN (False Negatives): Represents the count of ground truth steps that are not present in the predicted steps.
       Following this, we compute the precision, recall, and f-score.
       2. We will use the n-gram matching metrics: CIDEr [4], and SPICE [5]. Additionally, we plan to use sentence-level embedding-based metrics, BERTScore [6] as it captures the semantic similarity between the generated and ground truth captions.
    
    
    2. To compute the alignment between the predicted step segments and the ground truth step segments, we will use the intersection over union (IoU) metric. For a given step, IoU is computed as the ratio of the common segment to the union between the predicted and ground-truth segments. It ranges from 0 to 1. For the shorter step, where the step segment lasts, say, only 1-2 seconds, if the system-generated step segment does not match with the ground-truth segment, the system may end up with IoU=0. To deal with such a situation, we will use relaxed IoU, where we will extend the segments by λ before computing the IoU. We will compute the mean of the IoU for all the segments in the test set.